FA-50071 / PCM sample encoding / Open access

Pcm sample validity sideband: conceal state update · case 01

Invalid PCM amplitude contaminates the hold-last-valid concealment state.

Verified by executionVariant 1 · 8 checks per implementationDownload source bundle ↓JSON ↗

ROOT CAUSE

Invalid PCM amplitude contaminates the hold-last-valid concealment state.

VERIFIED REPAIR

Use the stated conversion contract at conceal state update.

Unsuccessful approach: Resetting to initial concealment ignores every valid update.

Case contract

Decode PCM with a parallel validity vector, missing flags invalid, holding the most recent valid sample for invalid positions while retaining explicit validity metadata.

Why this case matters

Offline PCM interchange uses these exact bounded packet and sample representation decisions.

1 / The failure

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(samples, validity, conceal):
    out=[]
    previous=conceal
    for index,sample in enumerate(samples):
        valid=validity[index] if index<len(validity) else False
        if not valid:
            previous=sample
        out.append([sample if valid else previous,bool(valid)])
    return [out,previous]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([1, 9, 3, 8], [True, False, True, False], 0)), [[[1, True], [1, False], [3, True], [3, False]], 3])
check('oracle 2', solve(*([9, 2], [False, True], 7)), [[[7, False], [2, True]], 2])
check('oracle 3', solve(*([1, 2, 3], [True], 0)), [[[1, True], [1, False], [1, False]], 1])
check('oracle 4', solve(*([], [], 4)), [[], 4])
check('oracle 5', solve(*([4, 5], [False, False], -1)), [[[-1, False], [-1, False]], -1])
check('oracle 6', solve(*([1, 2, 3], [False, True, False], 5)), [[[5, False], [2, True], [2, False]], 2])
check('oracle 7', solve(*([0], [True], 8)), [[[0, True]], 0])
if N == 1: check('variant packet 1', solve(*[[1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 2: check('variant packet 2', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 3: check('variant packet 3', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 4: check('variant packet 4', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 5: check('variant packet 5', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
oracle 1	`[[[1, True], [9, False], [3, True], [8, False]], 8]`	`[[[1, True], [1, False], [3, True], [3, False]], 3]`	Failed
oracle 2	`[[[9, False], [2, True]], 9]`	`[[[7, False], [2, True]], 2]`	Failed
oracle 3	`[[[1, True], [2, False], [3, False]], 3]`	`[[[1, True], [1, False], [1, False]], 1]`	Failed
oracle 4	`[[], 4]`	`[[], 4]`	Passed
oracle 5	`[[[4, False], [5, False]], 5]`	`[[[-1, False], [-1, False]], -1]`	Failed
oracle 6	`[[[1, False], [2, True], [3, False]], 3]`	`[[[5, False], [2, True], [2, False]], 2]`	Failed
oracle 7	`[[[0, True]], 8]`	`[[[0, True]], 0]`	Failed
variant packet 1	`[[[1, True], [9, False], [3, True], [8, False], [1, False], [9, False], [3, False], [8, False]], 8]`	`[[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False]], 3]`	Failed

SHA-256 / 0dc1a3a6e7cbe26582e8399951bf8c4904b4c166807ad8b21ca938c1533acc57

2 / The unsuccessful fix

Exit 1

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(samples, validity, conceal):
    out=[]
    previous=conceal
    for index,sample in enumerate(samples):
        valid=validity[index] if index<len(validity) else False
        if valid:
            previous=conceal
        out.append([sample if valid else previous,bool(valid)])
    return [out,previous]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([1, 9, 3, 8], [True, False, True, False], 0)), [[[1, True], [1, False], [3, True], [3, False]], 3])
check('oracle 2', solve(*([9, 2], [False, True], 7)), [[[7, False], [2, True]], 2])
check('oracle 3', solve(*([1, 2, 3], [True], 0)), [[[1, True], [1, False], [1, False]], 1])
check('oracle 4', solve(*([], [], 4)), [[], 4])
check('oracle 5', solve(*([4, 5], [False, False], -1)), [[[-1, False], [-1, False]], -1])
check('oracle 6', solve(*([1, 2, 3], [False, True, False], 5)), [[[5, False], [2, True], [2, False]], 2])
check('oracle 7', solve(*([0], [True], 8)), [[[0, True]], 0])
if N == 1: check('variant packet 1', solve(*[[1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 2: check('variant packet 2', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 3: check('variant packet 3', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 4: check('variant packet 4', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 5: check('variant packet 5', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
oracle 1	`[[[1, True], [0, False], [3, True], [0, False]], 0]`	`[[[1, True], [1, False], [3, True], [3, False]], 3]`	Failed
oracle 2	`[[[7, False], [2, True]], 7]`	`[[[7, False], [2, True]], 2]`	Failed
oracle 3	`[[[1, True], [0, False], [0, False]], 0]`	`[[[1, True], [1, False], [1, False]], 1]`	Failed
oracle 4	`[[], 4]`	`[[], 4]`	Passed
oracle 5	`[[[-1, False], [-1, False]], -1]`	`[[[-1, False], [-1, False]], -1]`	Passed
oracle 6	`[[[5, False], [2, True], [5, False]], 5]`	`[[[5, False], [2, True], [2, False]], 2]`	Failed
oracle 7	`[[[0, True]], 8]`	`[[[0, True]], 0]`	Failed
variant packet 1	`[[[1, True], [0, False], [3, True], [0, False], [0, False], [0, False], [0, False], [0, False]], 0]`	`[[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False]], 3]`	Failed

SHA-256 / 1cd36d12f1f962b86b9a414654edadaedff888c99b7490a7bb6bd8d587dd2c36

3 / The verified repair

Exit 0

"""Failure Map reference implementation. Python standard library only."""
import json

N = 1
observations = []
def solve(samples, validity, conceal):
    out=[]
    previous=conceal
    for index,sample in enumerate(samples):
        valid=validity[index] if index<len(validity) else False
        if valid:
            previous=sample
        out.append([sample if valid else previous,bool(valid)])
    return [out,previous]
def check(label, actual, expected):
    observations.append({"check": label, "actual": actual, "expected": expected, "passed": actual == expected})
check('oracle 1', solve(*([1, 9, 3, 8], [True, False, True, False], 0)), [[[1, True], [1, False], [3, True], [3, False]], 3])
check('oracle 2', solve(*([9, 2], [False, True], 7)), [[[7, False], [2, True]], 2])
check('oracle 3', solve(*([1, 2, 3], [True], 0)), [[[1, True], [1, False], [1, False]], 1])
check('oracle 4', solve(*([], [], 4)), [[], 4])
check('oracle 5', solve(*([4, 5], [False, False], -1)), [[[-1, False], [-1, False]], -1])
check('oracle 6', solve(*([1, 2, 3], [False, True, False], 5)), [[[5, False], [2, True], [2, False]], 2])
check('oracle 7', solve(*([0], [True], 8)), [[[0, True]], 0])
if N == 1: check('variant packet 1', solve(*[[1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 2: check('variant packet 2', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 3: check('variant packet 3', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 4: check('variant packet 4', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
if N == 5: check('variant packet 5', solve(*[[1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8, 1, 9, 3, 8], [True, False, True, False], 0]), [[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False], [3, False]], 3])
print(json.dumps({"observations": observations, "passed": all(x["passed"] for x in observations)}, ensure_ascii=False))
raise SystemExit(0 if all(x["passed"] for x in observations) else 1)

Boundary fixture	Actual	Expected	Outcome
oracle 1	`[[[1, True], [1, False], [3, True], [3, False]], 3]`	`[[[1, True], [1, False], [3, True], [3, False]], 3]`	Passed
oracle 2	`[[[7, False], [2, True]], 2]`	`[[[7, False], [2, True]], 2]`	Passed
oracle 3	`[[[1, True], [1, False], [1, False]], 1]`	`[[[1, True], [1, False], [1, False]], 1]`	Passed
oracle 4	`[[], 4]`	`[[], 4]`	Passed
oracle 5	`[[[-1, False], [-1, False]], -1]`	`[[[-1, False], [-1, False]], -1]`	Passed
oracle 6	`[[[5, False], [2, True], [2, False]], 2]`	`[[[5, False], [2, True], [2, False]], 2]`	Passed
oracle 7	`[[[0, True]], 0]`	`[[[0, True]], 0]`	Passed
variant packet 1	`[[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False]], 3]`	`[[[1, True], [1, False], [3, True], [3, False], [3, False], [3, False], [3, False], [3, False]], 3]`	Passed

SHA-256 / 2dd1ec5ab7d6345525f2aaaaf02989acc6d6f681dc9a15b2de8027d1b469bf76

Verification & scope

Stipulated finite model; no claim of hardware timing or full file-format conformance. This reproducer isolates one failure mechanism. Results cover the supplied fixtures. Variants within a family share a test contract and should remain grouped when constructing evaluation splits. Related mechanisms with a shared evaluation_group must also remain together; these controlled models are not independent production incidents.

Observations recorded using Python 3.12.14 at 2026-09-29T14:45:05.678062+00:00.

Case digest / e2ab101eb819f97809cbfa6c46449897334b18a2bdaa8a90ebf16f3d14e5f60d